Electrical pick-up



Dec. 2, 1930. W. D SMITH ELECTRICAL PICKUP Original Filed Dec. 23, 1925 A TTOR EYS.

Patented Dec. 2, 1930 UNITE STATES PATENT OFFICE WINFIELID I). SMITH, OF DEAL, NEV JERSEY, ASSIGNOR 'I'O LOUIS G. SYLVESTER, OF

' SCRANTON, PENNSYLVANIA ELECTRICAL PICK-UP Original application filed December 23,

My invention relates to transmitting devices for transmitting sound waves or impulses corresponding to sound waves. The most usual way of reproducing sound waves is by the use of a diaphragm. This general arrangement is open to many objections, for example the mechanical resistance of the dia phragm, and the fact that no diaphragm has lines of force in the magnetic field, will generate impulses of high potential which will accurately correspond to all tones and overtones impressed upon it, and this is particularly true because the vibrating member has no connection with a diaphragm or other mechanical contrivance. I have found by actual experiment that the above result always occurs, and as the wave impulses or similar impulses are impressed on the vibrating member, and corresponding electric impulses are produced, these, particularly because of their high potential, can be readily transmitted or can be amplified through any suitable amplifier, as for instance the tubes of a rad1o set, and then much amplified translated into audible sound. waves.

This application is a division of my pending application, Serial Number 77,329 filed December 23, 1925.

The present invention aims particularly to provide an electrical pick-up in which the armature member responds with great sensitivity and accuracy tothe sound waves impressed thereon, moving freely in response to the sound waves and without substantial flexure so that the'tones ultimately reproduced are pure and perfect and not marred by any impurities, due, for example, to the self-generated tones of an armature flexing 1925, Serial No. 77,329. Divided and this application filed March 1, 1928. Serial No. 258,212.

during movement. To this end, I support the armature yieldingly for free movement pivipgllout substantial flexure in the magnetic My invention is to be distinguished from the prior structures where the armature member itself has been in the form of'a tuning fork, flexing during its movements and thus setting up self-restoring forces and self-harmonics caused by the self-vibrations of the armature. My invention is also to be distinguished from the arrangements where the armature member is supported in or by a spring or flexible member which flexes during movement, exerts a restoring force on the armature and sets up self-vibrations also. In contradistinction to these arrangements, the armature member of this invention is supported for free movements without substantial flexure, and the supporting means is such that there is no substantial resisting force to the movement of the armature member, nor any appreciable self-vibrations set up therein and thus substantially the pure sound waves are produced by the apparatus.

Reference is to be had to the accompanying drawings forming a part of this specification,

' in which similar reference characters indicate corresponding parts in all the views.

Figure 1 is a plan View of a device embodying my invention.

Figure 2 is a broken'side elevation thereof.

Figure 3 is a broken detail section showing a means for improving the transmitted tone impulses.

Figure 4L- is a diagrammatic detail illustrating another means of trainsmitting the generated impulses and Figure 5 is a detail ofa modified and preferred way of mounting the vibrating member.

In practice I may use a permanent magnet 10 having spaced poles 11 and 12, but an electromagnet might be used without departing from the invention. I find, however, that a permanent magnet is simpler, answers all the requirements, and carries sufiicient magnetism to provide for the generation of electrical impulses as is well known in the sim ple forms of impulse generators. In the em bodiment shown, the magnet 10 serves as a frame for the device, and carries a cross piece 13 o1 insulation which secured to the frame or magnet 10, and has its ends further fastened by braces 1 1.

l vi brating' member acting like illlilllllilr ture, is spaced between the pole pieces 11 and 12 so that when vibrated it will cut the lines of force between the poles in the well known manner, and as a convenient means of supporting the member 15 l have provided it with a. brace 16 which is 'lastened to the cross piece 13. The loose mounting of cross-piece,

123, permits free movement of. the armature between the poles of the magnet without substantial flexure.

its a simple form of illustrating the invention and how it operates, I have shown the member 15 having a recessed end 17, and a binding screw 18 and adapted to receive a stylus 19 shown in dotted lines, which stylus can be of any approved type adapted to run in the grooves of a phonograph record disc. lVhen l have operated the device in connec tion with such a record disc, 1 have obtained results which have been remarkable, because I find that the stylus responds to all the wave impressions of the disc and transmits with great fidelity the impulse from every wave to the member 15 which vibrates in response to said waves, and each impulse results in a vibration causing the member 15 to cut through the magnetic field between the pole pieces 11 and 12, and the variations in magnetic flux are converted into electric impulses each of which corresponds to the sound or tone wave, and these can be transmitted as presently described.

I have found in practice that it is better to employ a sheath 20 of resilient material, for example rubber, or other material which can be placed upon the member 15, or at least introduced between the member and the ends of the pole pieces 11 and 12, and this has the etlect oit prewmting the vibrating member 15 from setting up persistent harmonics after the nature oi? those produced in av tuning :tork.

As a. convenient means of transmitting the impulses I can make a coil of wire 21 aroniul the base of the magnet 10 and have the leads J1-21 connect with any suitable amplifying device, as for example an audio amplifier set, or another way of transmitting the generated impulses is to have the member 15 vibrate in a coil 23 as shown in Figure l, and this can be provided. with leads 23-423 as illust water]. These various ways of transmitting the generated impulses are shown to make it evident that I am not limited to any means of transmitting these impulses, and 1 wish. to emphasize further the fact that the structure shown is only by way of example as clearly illustrating the invention, the principal feature of which isto have the member member 15 or similar member arranged to vibrate freely in a magnetic field, particularly between the pole pieces of a magnet, and to provide means for transn'iitting such generated impulses.

A preferred way of mounting or supporting the member 15, is shown in Fig. 5 where the member 15 is seated or embedded in a socket 2 1 of a soft rubber cushion 25 and the latter held in a keeper bracket 26 which is fastened to the brace 13. This arrangement insulates the member 15, and holds it resiliently to permit its free, universal vibration.

In. the example given I have shown the 15 responding to sound waves created by a stylus adapted to run in ,he grooves of a record disc or the like, but ohviously it does not matter so far as this invention is concerned how sound waves, or impulses corresponding to sound. waves, are impressed upon the member 15, the important thing being as stated, to make this member responsive to impulses oi the sound waves or t! air equivalent of all frequencies and to have it arranged and acting as stated.

I claim 1. An electrical pickup comprising a mag net, means for converting fluctuations in the magnetic flux; of the magnet .into electric current variations, a magnetic member disposed between the poles of opposite polarity of the magnet, yieldingly mounted means for yieldingly supporting said magnetic member to permit the same to move freely between the poles of the magnet without substantial flexnre, said supporting means being such as to permit movement of the magnetic member without setting up any appreciable restoring forces and without causing any substantial self-vibrations of the magnetic member, and means for vibrating the magnetic member in correspondence with the vibrations of sound waves.

2. An electrical pickup comprising a mag-- not having legs with poles of opposite polarity facing each other, means for converting fluctuations in the magnetic flux of the mag net into electric current variations, a magnetic member disposed between the poles of the magnet and supportedat only one end, a supporting member for the magnetic member yieldingly mounted across the legs of the mag not, and means for vibrating the. magnetic member in correspondencewith the vibrations of sound waves.

3. An electrical pickup comprising a U shaped magnet having poles facing each other, means for converting fluctuations in the magnetic flux of the magnetinto electric current variations, a magnetic member disposed between the poles of the magnet for movement therebet-ween, an insulating member yieldingly mounted across the poles of the magnet and supporting the magnetic member,

and means for vibrating the magnetic member in correspondence with the variations of sound waves.

4. An electrical pickup comprising a magnet, means for converting fluctuations in the magnetic flux of the magnet into electric current variations, a magnetic member disposed between the poles of opposite polarity of the magnet, yieldingly mounted insulating means supporting said magnetic member for free universal movement between the poles of the magnet without substantial fiexure, said supporting means being such as to permit movement of the magnetic member without setting up any appreciable restoring forces and without causing any substantial self-vibrations of the magnetic member, and means for vibrating the magnetic member in correspondence with the vibrations of sound waves.

5. An electrical pickup comprising means establishing a magnetic field, means for converting fluctuations in the flux of the field into electric current vibrations, a magnetic member in said field, a yieldingly mounted support magnetically insulated from said field supporting said magnetic member for free movement through said field without substantial fieXure, said supporting means being such as to permit movement of the magnetic member without setting up any appreciable restoring forces and without causing any substantial self-vibrations of the magnetic member, and means for vibrating the magnetic member in correspondence with the vibrations of sound waves.

In testimony whereof, I have signed my name to this specification this 28 day of Feb. 1928.

XVIN'FIELD D. SMITH. 

